In the past few years, because of providing a closed system that allowed for collection, transport, processing, sampling, and storage of specimens, serum separator tubes gained widespread acceptance gradually in China. However, some limitations associated with gel tubes had been observed, for example, gel and analyte stability. In order to circumvent these problems, a new tube (BD Vacutainer(R) SST(TM) II Plus (BD SST(TM) II Plus)) containing a new gel was released by BD with respect to analyte and gel stability. We investigated the performance of BD SST(TM) II Plus tubes for special proteins testing using BD Vacutainer(R) Serum Glass Tubes (BD Serum Glass) as controls. Equivalence between these two types of tubes was demonstrated for all analytes at initial time, and data for all analytes except complement 3 (C3) and complement 4 (C4) indicated comparable stability over time in these two types of tubes. Concentration of C3 and C4 tended to increase with preservation time up to 72 hr in BD Serum Glass tubes. The stability of C3 and C4 was better in BD SST(TM) II Plus, which was demonstrated at timepoints up to 48 hr. We conclude that BD SST(TM) II Plus was suitable for collection and storage of samples for special proteins testing. J. Clin. Lab. Anal. 25:203-206, 2011. (C) 2011 Wiley-Liss, Inc.